Precipitation Effects for Ka-band SAR

Kurzfassung

Space-borne Synthetic Aperture Radar (SAR) imaging is often considered to possess both
day/night and all weather operational capabilities. Whereas the first argument is true since we
are dealing with an active sensor; the second does not hold in cases for which the operating
frequencies are above ~ 3 GHz. Indeed, the SAR performance can be significantly affected by
atmospheric effects (losses), especially at unfavourable weather conditions. The principal
reason for the restriction on the use of these higher frequencies can be found in clear air losses
(water vapour and oxygen), cloud attenuation and attenuation due to precipitation, primarily rain.
The purpose of this interim report is to review, identify and assess the major propagation
effects in SAR imaging and investigate their relevance for the case of X-band and Ka-band
frequencies; i.e. the intention is to explain the underlying physical background of the effects,
especially the reflection and attenuation due to precipitation.